Cumulative Effects of Shoreline Armoring On Nearshore Systems Affecting Salmon Migration

In Puget Sound there are approximately 4,000 km of shoreline.  Pacific salmon use the nearshore of Puget Sound during migration.  Half of the salmon (Oncorhyncus) in Puget Sound are listed as threatened or endangered under the Endangered Species Act (ESA); this makes protecting and enhancing this migration corridor crucial for protection of the species.  Shoreline armoring is present along portions of Puget Sound to protect upland property from erosion.  This armoring creates a physical boundary between the terrestrial and marine ecosystem in Puget Sound that interacts with ecological systems at this ecotone to negatively affect salmon habitat.  In total, approximately 27% of shoreline in Puget Sound is backed by shoreline armoring, but areas with higher population tend to be the areas with the highest concentration of armoring.  There are many studies evaluating the effects of shoreline modifications on specific ecosystem functions such as hydrology, nutrient cycling, and sediment supply.  However, no known studies thoroughly synthesize these works to evaluate the potential for cumulative effects to salmonid species.  This systematic review concludes that the cumulative effect of impacts to multiple ecosystem functions may have a detrimental effect on salmon migration habitat, and points to areas for future research.